URGENT Joomla! hack fix job

This is an urgent requirment for a Joomla! experienced person who has expert knowledge in Joomla's security aspects. One of our sites is hacked and some junk of scripts have been installed in some PHP and HTML files. Sometimes, we found some .htaccess files too with some redirection scripts in it. We tried fixing it by cleaning and migrating to two different servers, but after installation few days later we have the same problem. This probably is small security issue that needs to be fixed. The provider must also tell us how to fix the problem. Payment Terms: Not more than $50 and will be paid one week after the fix - to make sure it does not get attacked again. If any further details needed, kindly PM. Happy Bidding!